The frequent scarcity of hydraulic resources intended for the irrigation of agricultural crops demands--and shall increasingly demand--a careful and sever administration of the same, using the suitable technical means to make compatible, a sever regulation of its consumption with the satisfaction of the hydric requirements of said crops.
Among the said means must be pointed out the drop irrigation, a method which consists of the distribution of water through a flexible pipe network, extended on the surface, in which a liquid out-put element is intercalated (dropper) which regulates it drop by drop, placed in such a way, that the debit is produced at the necessary location, that is to say, in the proximity of the stem of the plant or trunk of the tree being watered, so that it may absorb the water through the roots, with a practically total exploitation.
The out-put flow supplied by the dropper is proportional to the pressure of the fluid at the point of the pipe in which it is assembled; and the out-put section of all the droppers being constant in all the droppers whilst the pressure is variable depending on the height of the ground in which a determined dropper is installed, it results that, when the cultivated ground presents accentuated uneveness (for example, in layered cultivations) the droppers placed at low heights supply more water than those at high levels, with more and better benefit in the irrigation to the vegetables served and creating irregularities in the growth and production of the crop.
This disadvantage has been solved with the self-compensating droppers, in which the out-put section varies with reverse proportionality as regards the variations of the pressure, achieving that the irrigation flow is kept practically constant. This is attained by means of the use of a peripherical elastic membrane which supports on its exterior face the water pressure in the pipe in which the dropper is inserted, whilst on its internal face, adjacent to the out-put orifice, a reduced pressure acts when the liquid passes through a labyrinth which causes load loss.
With this arrangement, if the pressure in the piping system is relatively high at the point of insertion of the dropper, the membrane comes near the out-put orifice, reducing the feeding chamber and the pouring flow, acting in reverse if the pressure in the piping system is relatively low.
On the other hand, the conventional distribuition networks, extended on the surface, on the ground, are very vulnerable to land tilling operations, both manual and mecanical, increasing the risk of breakage of the piping system in this latter case due to circulation of agricultural vehicles.
Additionally, the effectiveness of the system may be negatively affected not only by the breaking of the piping system, but simply by its positional variation. In effect, the optical exploitation of the irrigation is conditioned by the proximity of the drop to the roots of the plant, in such a manner, that if the dropper is displaced from its position, which should be fixed and unvariable because the roots grow towards the wet ground and in the same, the irrigation may be wasted since it does not coincide with the majoritary and normal situation of the roots.
Due to all these reasons, the current tendency of the art is that of burying the piping systems with their droppers, creating underground distribution networks, with which its unvulnerability and immobility is obtained, with all the advantages inherent to the same.
However, this system also present a problem: the obstruction of the droppers when, due to a variation of the pressure in the piping systems, the liquid circulation direction is reversed in them, creating a depression at the out-put mouth of the dropper and a suction which, since the dropper is buried causes the penetration of earth in the same making it unusable.